Physicist James A. Van Allen's experiments in the late 1950s taught scientists to look at space in a whole new way: not as a vacuum but as a place pulsating with energy. Van Allen, who died Wednesday at age 91, discovered the belts of radiation surrounding the Earth that are now known as the Van Allen Belts.

The Voyager 1 spacecraft, is on the verge of slicing into interstellar space, NASA officials said today. Experts had thought the craft, launched in 1977, was at the solar system's edge back in 2003. That claim was disputed, but now all agree that the outer layer of the solar system is nigh.